‘If you break it, you buy it”: The left is now worried that the Pottery Barn rule may apply to the US health-care system. Sample whistling-in-the-dark headline from the lefty American Prospect: “Why ObamaCare Isn’t Like Iraq.”

But how could President Obama and Democrats botch it so badly? This is his signature achievement, the realization of generations of progressive dreaming. If it really fails, they’ll be paying a political price for decades.

The answer’s obvious: None of them ever bothered much about actually making it work.

It was all about ramming it through, with short-term political needs dictating everything.

They never engaged their critics; they either bought them off or demonized them. Every lobbyist was focused on getting the best possible deal for his industry; dubious Democrats got their special-interest provisions, like the Cornhusker Kickback.

And they end-ran the legislative process: Remember, the bill that became law was just Sen. Max Baucus’ rough draft. The Senate passed it as an “offer” to the House — but then Massachusetts voters sent Scott Brown to Washington to stop the madness, and Democrats’ only option for getting it to Obama’s desk was to stick with the draft.

This, recall, was when then-Speaker Nancy Pelosi made her infamous “We have to pass the bill so that you can find out what’s in it” comment. Too true, Nancy, too true.

That law was a kludge of ideas, some old, some new — and a lot of them contradictory. (If you’re trying to contain costs, don’t order every insurance policy to cover more stuff than most of them do now.)

Nobody thought it through. Clearly, no one asked if they’d need a Web site, and how long it might take the feds to create a functional one. The deadlines were all about politics — e.g., not starting it for a couple of years so the talking points could obscure the actual costs.

Find this hard to believe? Remember, the same president and Congress gave us a $900 billion stimulus centered on “shovel-ready jobs” — only to tell us a couple of years later that, oops, there actually weren’t all that many shovel-ready jobs.

Heck, they didn’t even stop to ask if ObamaCare was constitutional. (It probably isn’t — but Chief Justice John Roberts plainly decided that striking it down would risk destroying the Supreme Court, so he let it live. Yay?)

Plus, the administration put off a lot of key decisions until after November 2012, lest something unpopular endanger Obama’s re-election. The decisions it did make, and announce loudly, were all politically motivated shout-outs — like the ruling that, yes, every policy must cover abortion and birth control, which was ammunition for the “War on Women” attack on Mitt Romney.

And all along, everybody thought of it as 1) a new program and 2) an entitlement.

The dirty secret of a new government program is that it doesn’t really have to work at all well: It helps some people, both the direct beneficiaries and all the soon-politically powerful folks who get paid to provide the help (Hello, Vito Lopez! Hello, ethanol makers!), and the costs just get buried in this year’s borrowing from China.

And new entitlements are supposedly immortal — people get addicted to subsidies, which they quickly believe are their right. That’s why, ever since it passed, liberals have been telling each other that ObamaCare’s popularity had to turn net positive once it finally kicked in.

Oops: They failed to realize that they were “giving” Americans something that most of us already had — so we had damn well better see the “gift” as better than what they’re taking away. Which means it actually has to work, and not just as a talking point.

For now, the administration and most Democrats are in fingers-crossed Hail Mary mode: Maybe, somehow, it’ll work well enough to muddle forward. (Hey, no one’s gotten rid of the Transportation Security Administration, right?)

Maybe they’ll re-take the House so they can pass legislation to fix it. (You’re already seeing grumbling on the left that “single payer” would work better, as if a bunch that can’t contract out the design of a Web site would somehow be able to run the entire US health-care system themselves.)

Maybe they can somehow convince enough people that it’s the Republicans’ fault, or the insurance companies’.

On the other hand, maybe they’ll wind up paying a stiff price at the polls for a generation over the biggest, most foolish overreach in the history of American politics.